To document the long-term safety profile of MMF 1g bid in patients with rheumatoid arthritis. This study is a follow up study to SPID# 0360. Mycophenolate mofetil (RS 61443) (MMF) is an immunosuppressant that reversibly inhibits the proliferative response of human peripheral mononuclear cells to T and B cell mitogens in Vitro, and immunoglobulin formation by human B cells in response to polyclonal stimulators. These properties make MMF a good candidate for use in patients with rheumatoid arthritis (RA). Phase I and II data indicated that optimum effect and safety were achieved at a MMF dose of 1 g BID in patients with RA. The Study is an extension of the "double-blind, randomized, parallel group, multicenter comparison of the efficacy and safety of mycophenolate mofetil and placebo in patients with active rheumatoid arthritis" (asscession #97-7174). The design in an open-label trial of MMF therapy in RA for a minimum of 6 months and will have a duration of approximately 1 year, evaluating the long-term safety profile. Seven patients are anticipated at Massachusetts General Hospital to continue into this extension study.